README.md

libft-asm

Part 1

• bzero
• strcat
• isalpha
• isdigit
• isalnum
• isascii
• isprint
• toupper
• tolower
• puts (obviously, you can use the write syscall)

Part 2

• strlen
• memset
• memcpy
• strdup (obviously you are allowed to call malloc)

Part 3

To conclude, you must code a ft_cat function which will take a file descriptor (for example 0...) as argument and that will have the same behavior as the cat command it’ll return void.

Nasm on macOS

• Stack must be 16-bit aligned.
• Symbols must be prefixed with an underscore (e.g. _printf).
• Syscalls on x86_64 uses the same opcodes as x86.
• Syscall opcodes must be offset by x200000, i.e. a syscall to write (usually 0x4) would be 0x2000004 (2, five 0's, 4).

Useful articles

Tutorial on nasm assembly, covers plenty of topics:

• http://cs.lmu.edu/~ray/notes/nasmtutorial/

Stack?

• https://eli.thegreenplace.net/2011/02/04/where-the-top-of-the-stack-is-on-x86/
• https://eli.thegreenplace.net/2011/09/06/stack-frame-layout-on-x86-64/

Sample code:

• https://www.csee.umbc.edu/portal/help/nasm/sample_64.shtml

Complete tutorial (lots of useful information but overall not extremely reliable information):

• https://www.tutorialspoint.com/assembly_programming/index.htm
• https://www.tutorialspoint.com/assembly_programming/assembly_strings.htm (especially useful for mem* operations like memcpy (see next point!))

strlen (a little extra info on rep and scasb):

• https://osandamalith.com/2016/11/08/string-length-function-in-nasm/

Syscalls/interfacing with Linux:

• https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux#syscall
• https://syscalls64.paolostivanin.com/

Architecture (describes register purposes):

• https://en.wikibooks.org/wiki/X86_Assembly/X86_Architecture

x86 opcode and instruction set reference:

• http://ref.x86asm.net/ (see the table near the top of the page for the differences between the versions)

Not exactly sure what this is but I used the x86-64 psABI version 1.0 document for register reference on p. 23 (version 1, Jan 28, 2018). The document contains a lot of information on the x86-64 architecture:

• https://github.com/hjl-tools/x86-psABI/wiki/X86-psABI

Debugging:

• Debugging x86-64 assembly with lldb and dtrace

Some answers that cleared up confusion for me:

• LEA vs MOV

And, of course, there is always the official documentation:

• nasm (available in pdf and html format)
• Intel assembly (also available in pdf format, link at the top of the article)
• Intel® 64 and IA-32 Architectures Software Developer’s Manual (all volumes)